The invention relates to air filters for automotive engines, and more particularly to an improved, self-contained air filter assembly for a fuel injected engine, eliminating the need for a canister or housing as has typically been used on such engines.
In fuel injected engines, filtration of ingested air must be very complete in order to avoid interference of even very small particles with the relatively sophisticated and fine-tuned components of the injection system. Generally, fuel injected systems as incorporated on many high-performance European cars have included a rectangular air intake opening with a canister type air filter assembly connected to the opening and a cartridge type replaceable air filter unit inside the canister. The canisters have usually included a relatively small horn-shaped opening through which all the intake air must pass as it enters the canister for distribution around the surfaces of the filtering element inside. This type of assembly has been expensive to produce and to maintain, and has resulted in sometimes serious restrictions of the air supply to the engine, due to the narrowness of the air filter housing opening, the flow paths required for entry into the filter element, and the type of filter element employed, usually porous paper. The disposable filter element had to be changed quite frequently and even the filter housing, which sometimes was of plastic, usually required periodic replacement because of permanent deformation due to engine heat. The deformed housing would no longer seal against the intake opening, and unfiltered air would be admitted to the engine. On some automobiles, elastic bands were used to hold the filter housing in place on the filter seat, connected to projections on the sides of the filter seat, and these bands would frequently fail.
There have been marketed several replacement air filters, particularly for carbureted engines, comprised of cleanable foam material supported by appropriate air-permeable retaining structure, with no external housing or canister needed. These filters have generally reduced air resistance into the engine and have sometimes been claimed to improve performance on carbureted engines.
However, there has been a need for a simpler, more economically produced air filter assembly for highly tuned fuel injected engines, which does not unduly restrict airflow and which is quickly and easily mounted on and removed from the air intake filter seat and capable of cleaning and re-use.